Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micro-meters or smaller. One area in which micro-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, micro-fabrication becomes increasingly important. Micro-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which micro-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.
An exemplary micro-fabrication includes forming a relief image in a structure by depositing a polymerizable fluid composition onto a transfer layer. The transfer layer may be a sacrificial layer providing a mask for patterning the substrate or the substrate itself. A mold makes mechanical contact with the polymerizable fluid. The mold includes a relief structure, and the polymerizable fluid composition fills the relief structure. The polymerizable fluid composition is then subjected to conditions to solidify and polymerize the same, forming a solidified polymeric material on a transfer layer that contains a relief structure complimentary to that of the mold. The mold is then separated from the solid polymeric material such that a replica of the relief structure in the mold is formed in the solidified polymeric material. The solidified polymeric material is subjected to an environment to selectively etch the transfer layer relative to the solidified polymeric material such that a relief image is formed in the transfer layer. With this process, patterns with features on the scale of a few nanometers may be formed. As a result, substrates demonstrate extreme topologies when compared to the dimensions of features formed thereon may prevent accurate reproduction of the pattern in the solidified polymeric layer. Substrates formed from gallium arsenide (GAs) or indium phosphide (InP) have typically been found to demonstrate extreme topologies.
One manner in which to reduce, if not avoid, the effects of extreme topologies is demonstrated in U.S. Pat. No. 6,334,960 to Willson et al. Willson et al. disclose a method of forming a relief image in a structure that includes providing a substrate having a planarization layer. The planarization layer provides a substantially planar surface upon which a polymerizable fluid composition is deposited. Thereafter, a mold, having a relief structure, makes mechanical contact with the polymerizable fluid composition. The polymerizable fluid composition fills the relief structure. The polymerizable fluid composition is then subjected to conditions to solidify and polymerize the same, forming a solidified polymeric material on the planarization layer that contains a relief structure complimentary to that of the mold. The mold is then separated from the solid polymeric material such that a replica of the relief structure in the mold is formed in the solidified polymeric material. The planarization layer and the solidified polymeric material are subjected to an environment to selectively etch the planarization layer relative to the solidified polymeric material such that the relief image is transferred into the planarization layer.
It is desired, therefore, to provide improved techniques for pattern substrates having non-planar surfaces employing imprint lithography processes.